[News] 5dmk3 Light Leak Issue Surfaces

It seems a new issue has popped up for the Canon 5dmk3. Multiple people are reporting that there is a light leak through the top LCD panel that directly affects metering. The easiest way to detect this issue is to put the body cap on the camera body as well as cover the viewfinder. Then place the camera in "P" mode at ISO800 and press the LCD backlight button.

As you can see in the video, the shutter speed changes depending on whether the backlight is activated. Similar results are achieved when a flashlight is shone onto the top LCD. Some users are even reporting that direct sunlight or walking into a room with bright overhead light is enough to sway the meter. If you are one of the lucky ones who managed to purchase a 5dmk3, it might be worth doing this little test to see if you need to seek a replacement version.

Test Procedure:
Remove lens and place the body cap on the camera body.
Place the viewfinder cover on the viewfinder.
(This should theoretically block any light from entering the camera.)
Set ISO to 800 and set the camera mode to "P".
(You should see a shutter speed of around 10 sec.)
Now either shine a flashlight near the top LCD panel area or simply turn on the backlight for the top LCD panel.
This will cause the shutter speed to fluctuate between 5-8 seconds, indicating light leakage.

Guys! Have you tried this on the Canon EOS 5D Mark II? Guess what... it isn't a new issue. The 5D2 does the same thing and it isn't a light leak thru the LCD - it is an issue with light leaking thru the viewfinder. That's why there's a rubber cap to go over the viewfinder that comes with the camera.

I put my 5D2 thru the same tests and the 5D2 does the same... cover up the viewfinder and guess what... no exposure changes!

From page 114 of the Canon 5D Mk III manual (and, coincidentally, page 86 of the Mk II manual):"If you will not look through the viewfinder when you press the shutter button, attach the eyepiece cover (p.185). If stray light enters the viewfinder when the picture is taken, it may throw off the exposure."

Did you miss the part where they covered the viewfinder and still got this problem?

Light leaking from the viewfinder is a problem that has ALWAYS existed on SLR's, and that's why expensive camera bodies has ha switch on the side that lets you cover the viewfinder without attaching a cap. My Nikon F2 (a model that came 1971) has this.

What is shown in these videos is not light from the viewfinder, but from the LCD area.

Ok, after reading the DPreview forum posts and trying some of my own tests... I'm not concerned. Maybe if you're doing long exposure night photography you'll want to not shine a light on the LCD area... but even so, nobody's shown that it impacts the photo being taken... maybe just gives the wrong exposure.

but even so, nobody's shown that it impacts the photo being taken... maybe just gives the wrong exposure.

Ehhm, perhaps that's exactly what impacts the photo being taken: exposure is off by 2/3 - 1 stop. And yes: this is an issue when you're in the right circumstances (images at night, photographing people at a reception when you're just under a bulb, etc).

I agree that this won't be a problem at your usual outdoor situation, but please do keep in mind that the 5d and successors are being used rather a lot by wedding photographers... If you are at iso6400 or higher and your exposure is 1 stop off you probably won't like your result.

It isn't clear here if this is only affecting the meter reading, or if there is actually light falling on the sensor that would corrupt a long night exposure. If the former, than I am not concerned (yes, I have a MK III). For those night shots, I don't rely on the meter reading anyway.

However, if this actually means that the star-trails shots will have a haze or perhaps a corner that is ruined by spill light, then I am not happy at all... I've only had the camera a couple days, and haven't had a chance for any night shots yet. So far I am very happy with the studio performance of the camera.

Just to be clear, it doesn't HAVE to be a light leak. Electronics used to Light the LCD could be drawing current that then drops the sensors current for Metering and causes it to misinterpret the true reading and give a false meter reading.

I think it's good we found out now, that if you're going to take a photo without a lens, and just a lens mount cover on, at night, at iso 800, with the view finder covered, you better not use the lcd illuminator, or you may not get the pic.... :-)

I just tested both my MK III and my older MK II. The MK III _did_ exhibit this effect, though not as much as the original report. Mine went from 4 sec to 3.2 sec in the test. The older MK II had no change at all.

Again, if it is a meter reading only, I am not really worried. After all, if the body cap is on and there is NO light at all coming in, then an exposure of 4 sec at ISO 800 won't show anything anyway. That is why I don't use the meter for night or special effects shots.

I have seen several night/high-ISO shots in online reviews, and none seem damaged by this. Haven't done those myself yet with my new camera (just got it a couple days ago), but can't really say I am all that worried. I expect Canon will come up with some firmware fix to this molehill-as-mountain problem. In the meantime, I will just revel in my new-toy-happiness... :)